There are defiantly some additional ways to gain entrance into tertiary institutions other than through completion of year 13.

If you have not studied beyond Year 12, you may be eligible for discretionary entrance providing you meet the required criteria.

I have attached some information below which directly relates to discretionary entrance from the Universities NZ site.

Discretionary Entrance

The Discretionary Entrance Regulations were published in July 2002 and came into force in 2003. They provide a route to university study for students who have not continued secondary education beyond Year 12. The chief features of the regulations are as follows:

They apply only to New Zealand or Australian citizens and permanent residents under 20 years of age.

Applicants must have a minimum of 14 credits in an approved subject at Level 2 towards NCEA.

Applicants must also have met the literacy and numeracy standards required for University Entrance.

Application must be made to the university of choice and a fee may be payable.

A reference from a school principal or other suitable person is required and there may be an interview.

Students who have undertaken Year 13 study beyond 1 June in any year are ineligible to apply in the same year but may be considered for mid-year admission in the following year.